Method for coating a substrate

Abstract

A method for coating a substrate includes the steps of: forming a conductive coating layer on a surface of a substrate so as to form a semi-product; submerging a conductive sheet and the semi-product into an electrophoresis medium that includes charged colloid particles; and applying a voltage on the conductive sheet or the semi-product to form an electric field among the conductive sheet, the semi-product, and the electrophoresis medium, so that the colloid particles move along the electric field toward the semi-product and an electrophoretic covering layer formed by the charged colloid particles is thus deposited on the electrophoretic covering layer.

What is claimed is: 
     
       1. A method for coating a substrate, comprising the steps of:
 forming a conductive coating layer on at least a part of a surface of the substrate so as to form a semi-product, the conductive coating layer being made of a conductive lacquer and having a surface resistance no greater than 500 Ω·m; 
 submerging a conductive sheet and the semi-product into an electrophoresis medium that includes charged colloid particles, the conductive sheet and the semi-product functioning as electrodes; and 
 applying a voltage ranging between 60V and 120V on one of the conductive sheet and the semi-product to form an electrical field among the conductive sheet, the semi-product and the electrophoresis medium, so that a part of the charged colloid particles move along a direction of the electric field toward the semi-product and an electrophoretic covering layer formed by the charged colloid particles is thus deposited on the conductive coating layer, the electrophoretic covering layer having a thickness no greater than 30 μm. 
 
     
     
       2. The method according to  claim 1 , wherein a total thickness of the conductive coating layer and the electrophoretic covering layer is no greater than 50 μm. 
     
     
       3. The method according to  claim 1 , wherein
 the conductive lacquer includes a base material and a conductive material, 
 the base material is one of an epoxy resin and an acrylic resin, and 
 the conductive material is one of modified titanium oxide, metal, carbon-nanotube, graphite, and graphene. 
 
     
     
       4. The method according to  claim 3 , wherein the conductive lacquer further includes a colorant that is one of an inorganic pigment and an organic dye. 
     
     
       5. The method according to  claim 1 , wherein the substrate is made of a material which is one of magnesium, aluminum, magnesium alloy, aluminum alloy, and magnesium-aluminum alloy. 
     
     
       6. The method according to  claim 1 , wherein the charged colloid particles of the electrophoresis medium is a waterborne resin. 
     
     
       7. The method according to  claim 1 , wherein the voltage ranges from 80 v to 120 v. 
     
     
       8. The method according to  claim 7 , wherein the voltage ranges from 80 v to 100 v. 
     
     
       9. The method according to  claim 1 , wherein the step of forming the conductive coating layer on at least the part of the surface of the substrate is conducted by coating technique.